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N
IGHT VISION
Generally, most pilots are poorly informed about night Cones for:
vision. Human eyes never function as effectively at • Color
• Detail
night as the eyes of animals with nocturnal habits, but
• Day
if humans learn how to use their eyes correctly and
know their limitations, night vision can be improved
significantly. There are several reasons for training to
use the eyes correctly.
Rods for:
One reason is the mind and eyes act as a team for a per- • Gray
son to see well; both team members must be used • Peripheral
• Day & Night
effectively. The construction of the eyes is such that to
see at night they are used differently than during the
day. Therefore, it is important to understand the eye’s
construction and how the eye is affected by darkness.
Innumerable light-sensitive nerves, called “cones” and
“rods,” are located at the back of the eye or retina, a
layer upon which all images are focused. These nerves Area of Best
Day Vision
connect to the cells of the optic nerve, which transmits
messages directly to the brain. The cones are located in
the center of the retina, and the rods are concentrated
in a ring around the cones. [Figure 10-1]
The function of the cones is to detect color, details, and
faraway objects. The rods function when something is
seen out of the corner of the eye or peripheral vision.
Area of Best
They detect objects, particularly those that are moving,
Night Vision
but do not give detail or color—only shades of gray.
Both the cones and the rods are used for vision during
daylight.
Area of Best
Although there is not a clear-cut division of function,
Night Vision
the rods make night vision possible. The rods and
cones function in daylight and in moonlight, but in the
absence of normal light, the process of night vision is
placed almost entirely on the rods.
Figure 10-1.Rods and cones.
The fact that the rods are distributed in a band around The eye’s adaptation to darkness is another important
the cones and do not lie directly behind the pupils aspect of night vision. When a dark room is entered, it
makes off-center viewing (looking to one side of an is difficult to see anything until the eyes become
object) important during night flight. During daylight, adjusted to the darkness. Most everyone has experi-
an object can be seen best by looking directly at it, but enced this after entering a darkened movie theater. In
at night a scanning procedure to permit off-center this process, the pupils of the eyes first enlarge to
viewing of the object is more effective. Therefore, the receive as much of the available light as possible. After
pilot should consciously practice this scanning proce- approximately 5 to 10 minutes, the cones become
dure to improve night vision. adjusted to the dim light and the eyes become 100
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times more sensitive to the light than they were before • Close one eye when exposed to bright light to
the dark room was entered. Much more time, about 30 help avoid the blinding effect.
minutes, is needed for the rods to become adjusted to
darkness, but when they do adjust, they are about • Do not wear sunglasses after sunset.
100,000 times more sensitive to light than they were in
the lighted area. After the adaptation process is com- • Move the eyes more slowly than in daylight.
plete, much more can be seen, especially if the eyes are
used correctly. • Blink the eyes if they become blurred.
After the eyes have adapted to the dark, the entire • Concentrate on seeing objects.
process is reversed when entering a lighted room. The
eyes are first dazzled by the brightness, but become • Force the eyes to view off center.
completely adjusted in a very few seconds, thereby los-
ing their adaptation to the dark. Now, if the dark room • Maintain good physical condition.
is reentered, the eyes again go through the long process
of adapting to the darkness. • Avoid smoking, drinking, and using drugs that
may be harmful.
The pilot before and during night flight must consider
the adaptation process of the eyes. First, the eyes N
IGHT ILLUSIONS
should be allowed to adapt to the low level of light
In addition to night vision limitations, pilots should be
and then they should be kept adapted. After the eyes
aware that night illusions could cause confusion and
have become adapted to the darkness, the pilot should
concerns during night flying. The following discus-
avoid exposing them to any bright white light that
sion covers some of the common situations that cause
will cause temporary blindness and could result in
illusions associated with night flying.
serious consequences.
On a clear night, distant stationary lights can be mis-
Temporary blindness, caused by an unusually bright
taken for stars or other aircraft. Even the northern
light, may result in illusions or after images until the
lights can confuse a pilot and indicate a false horizon.
eyes recover from the brightness. The brain creates
Certain geometrical patterns of ground lights, such as
these illusions reported by the eyes. This results in
a freeway, runway, approach, or even lights on a mov-
misjudging or incorrectly identifying objects, such as
ing train can cause confusion. Dark nights tend to
mistaking slanted clouds for the horizon or populated
eliminate reference to a visual horizon. As a result,
areas for a landing field. Vertigo is experienced as a
pilots need to rely less on outside references at night
feeling of dizziness and imbalance that can create or
and more on flight and navigation instruments.
increase illusions. The illusions seem very real and
pilots at every level of experience and skill can be
Visual autokinesis can occur when a pilot stares at a
affected. Recognizing that the brain and eyes can play
single light source for several seconds on a dark night.
tricks in this manner is the best protection for flying at
The result is that the light will appear to be moving.
night.
The autokinesis effect will not occur if the pilot
expands the visual field. It is a good procedure not to
Good eyesight depends upon physical condition.
become fixed on one source of light.
Fatigue, colds, vitamin deficiency, alcohol, stimulants,
smoking, or medication can seriously impair vision.
Distractions and problems can result from a flickering
Keeping these facts in mind and taking adequate pre-
light in the cockpit, anticollision light, strobe lights,
cautions should safeguard night vision.
or other aircraft lights and can cause flicker vertigo. If
continuous, the possible physical reactions can be
In addition to the principles previously discussed, the
nausea, dizziness, grogginess, unconsciousness,
following items will aid in increasing night vision
headaches, or confusion. The pilot should try to elim-
effectiveness.
inate any light source causing blinking or flickering
problems in the cockpit.
• Adapt the eyes to darkness prior to flight and
keep them adapted. About 30 minutes is needed
A black-hole approach occurs when the landing is
to adjust the eyes to maximum efficiency after
made from over water or non-lighted terrain where the
exposure to a bright light.
runway lights are the only source of light. Without
• If oxygen is available, use it during night flying. peripheral visual cues to help, pilots will have trouble
Keep in mind that a significant deterioration in orientating themselves relative to Earth. The runway
night vision can occur at cabin altitudes as low as can seem out of position (downsloping or upsloping)
5,000 feet. and in the worse case, results in landing short of the
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runway. If an electronic glide slope or visual approach The lights of cities and towns can be seen at surprising
slope indicator (VASI) is available, it should be used. distances at night, and if this adjacent chart is not avail-
If navigation aids (NAVAIDs) are unavailable, careful able to identify those landmarks, confusion could
attention should be given to using the flight instru- result. Regardless of the equipment used, organization
ments to assist in maintaining orientation and a normal of the cockpit eases the burden on the pilot and
approach. If at any time the pilot is unsure of his or her enhances safety.
position or attitude, a go-around should be executed.
A
IRPLANE EQUIPMENT
Bright runway and approach lighting systems, espe- AND LIGHTING
cially where few lights illuminate the surrounding Title 14 of the Code of Federal Regulations (14 CFR)
terrain, may create the illusion of less distance to the part 91 specifies the basic minimum airplane equip-
runway. In this situation, the tendency is to fly a ment required for night flight. This equipment includes
higher approach. Also, when flying over terrain with only basic instruments, lights, electrical energy source,
only a few lights, it will make the runway recede or and spare fuses.
appear farther away. With this situation, the tendency
is common to fly a lower-than-normal approach. If The standard instruments required for instrument
the runway has a city in the distance on higher ter- flight under 14 CFR part 91 are a valuable asset for
rain, the tendency will be to fly a lower-than-normal aircraft control at night. An anticollision light system,
approach. Agood review of the airfield layout and including a flashing or rotating beacon and position
boundaries before initiating any approach will help lights, is required airplane equipment. Airplane posi-
the pilot maintain a safe approach angle. tion lights are arranged similar to those of boats and
ships. Ared light is positioned on the left wingtip, a
Illusions created by runway lights result in a variety of green light on the right wingtip, and a white light on
problems. Bright lights or bold colors advance the run- the tail. [Figure 10-2]
way, making it appear closer.
Night landings are further complicated by the difficulty
of judging distance and the possibility of confusing
approach and runway lights. For example, when a dou-
ble row of approach lights joins the boundary lights of
the runway, there can be confusion where the approach
lights terminate and runway lights begin. Under certain
conditions, approach lights can make the aircraft seem
higher in a turn to final, than when its wings are level.
P
ILOT EQUIPMENT
Before beginning a night flight, carefully consider
personal equipment that should be readily available
during the flight. At least one reliable flashlight is
recommended as standard equipment on all night
flights. Remember to place a spare set of batteries in
the flight kit. A D-cell size flashlight with a bulb
switching mechanism that can be used to select white
Figure 10-2.Position lights.
or red light is preferable. The white light is used while
performing the preflight visual inspection of the airplane, This arrangement provides a means by which pilots
and the red light is used when performing cockpit opera- can determine the general direction of movement of
tions. Since the red light is nonglaring, it will not impair other airplanes in flight. If both a red and green light of
night vision. Some pilots prefer two flashlights, one another aircraft were observed, the airplane would be
with a white light for preflight, and the other a pen- flying toward the pilot, and could be on a collision
light type with a red light. The latter can be suspended course.
by a string from around the neck to ensure the light is
always readily available. One word of caution; if a red Landing lights are not only useful for taxi, takeoffs,
light is used for reading an aeronautical chart, the red and landings, but also provide a means by which air-
features of the chart will not show up. planes can be seen at night by other pilots. The Federal
Aviation Administration (FAA) has initiated a volun-
Aeronautical charts are essential for night cross-coun- tary pilot safety program called “Operation Lights
try flight and, if the intended course is near the edge of ON.” The “lights on” idea is to enhance the “see and
the chart, the adjacent chart should also be available. be seen” concept of averting collisions both in the air
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and on the ground, and to reduce the potential for bird by dual peaked (two quick) white flashes, then
strikes. Pilots are encouraged to turn on their landing green.
lights when operating within 10 miles of an airport.
This is for both day and night, or in conditions of Beacons producing red flashes indicate obstructions or
reduced visibility. This should also be done in areas areas considered hazardous to aerial navigation.
where flocks of birds may be expected. Steady burning red lights are used to mark obstruc-
tions on or near airports and sometimes to supplement
Although turning on aircraft lights supports the see and flashing lights on en route obstructions. High intensity
be seen concept, pilots should not become complacent flashing white lights are used to mark some supporting
about keeping a sharp lookout for other aircraft. Most structures of overhead transmission lines that stretch
aircraft lights blend in with the stars or the lights of the across rivers, chasms, and gorges. These high intensity
cities at night and go unnoticed unless a conscious lights are also used to identify tall structures, such as
effort is made to distinguish them from other lights. chimneys and towers.
A
IRPORT AND NAVIGATION As a result of the technological advancements in
LIGHTING AIDS aviation, runway lighting systems have become
The lighting systems used for airports, runways, quite sophisticated to accommodate takeoffs and
obstructions, and other visual aids at night are other landings in various weather conditions. However,
important aspects of night flying. the pilot whose flying is limited to VFR only needs
to be concerned with the following basic lighting of
Lighted airports located away from congested areas runways and taxiways.
can be identified readily at night by the lights outlining
the runways. Airports located near or within large The basic runway lighting system consists of two
cities are often difficult to identify in the maze of straight parallel lines of runway-edge lights defin-
lights. It is important not to only know the exact loca- ing the lateral limits of the runway. These lights are
tion of an airport relative to the city, but also to be able aviation white, although aviation yellow may be
to identify these airports by the characteristics of their substituted for a distance of 2,000 feet from the far
lighting pattern. end of the runway to indicate a caution zone. At
some airports, the intensity of the runway-edge
Aeronautical lights are designed and installed in a vari-
lights can be adjusted to satisfy the individual needs
ety of colors and configurations, each having its own
of the pilot. The length limits of the runway are
purpose. Although some lights are used only during
defined by straight lines of lights across the runway
low ceiling and visibility conditions, this discussion
ends. At some airports, the runway threshold lights
includes only the lights that are fundamental to visual
are aviation green, and the runway end lights are
flight rules (VFR) night operation.
aviation red.
It is recommended that prior to a night flight, and
At many airports, the taxiways are also lighted. Ataxi-
particularly a cross-country night flight, the pilot check
way-edge lighting system consists of blue lights that
the availability and status of lighting systems at the
outline the usable limits of taxi paths.
destination airport. This information can be found on
aeronautical charts and in the Airport/Facility
P
Directory. The status of each facility can be deter- REPARATION AND PREFLIGHT
mined by reviewing pertinent Notices to Airmen Night flying requires that pilots be aware of, and oper-
(NOTAMs). ate within, their abilities and limitations. Although
careful planning of any flight is essential, night flying
Arotating beacon is used to indicate the location of
demands more attention to the details of preflight
most airports. The beacon rotates at a constant speed,
preparation and planning.
thus producing what appears to be a series of light
flashes at regular intervals. These flashes may be one
Preparation for a night flight should include a thorough
or two different colors that are used to identify various
review of the available weather reports and forecasts
types of landing areas. For example:
with particular attention given to temperature/dewpoint
spread. Anarrow temperature/dewpoint spread may
• Lighted civilian land airports—alternating white
indicate the possibility of ground fog. Emphasis
and green.
should also be placed on wind direction and speed,
• Lighted civilian water airports—alternating since its effect on the airplane cannot be as easily
white and yellow. detected at night as during the day.
• Lighted military airports—alternating white and On night cross-country flights, appropriate aero-
green, but are differentiated from civil airports nautical charts should be selected, including the
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appropriate adjacent charts. Course lines should be of the airplane can be detected easily. At night, the
drawn in black to be more distinguishable. airplane could creep forward without being noticed
unless the pilot is alert for this possibility. Hold or
Prominently lighted checkpoints along the prepared lock the brakes during the runup and be alert for any
course should be noted. Rotating beacons at airports, forward movement.
lighted obstructions, lights of cities or towns, and
T
lights from major highway traffic all provide excellent AKEOFF AND CLIMB
visual checkpoints. The use of radio navigation aids Night flying is very different from day flying and
and communication facilities add significantly to the demands more attention of the pilot. The most notice-
safety and efficiency of night flying. able difference is the limited availability of outside
visual references. Therefore, flight instruments should
All personal equipment should be checked prior to
be used to a greater degree in controlling the airplane.
flight to ensure proper functioning. It is very discon-
This is particularly true on night takeoffs and climbs.
certing to find, at the time of need, that a flashlight, for
The cockpit lights should be adjusted to a minimum
example, does not work.
brightness that will allow the pilot to read the instru-
ments and switches and yet not hinder the pilot’s out-
All airplane lights should be turned ON momentarily
side vision. This will also eliminate light reflections on
and checked for operation. Position lights can be
the windshield and windows.
checked for loose connections by tapping the light fix-
ture. If the lights blink while being tapped, further
After ensuring that the final approach and runway are
investigation to determine the cause should be made
clear of other air traffic, or when cleared for takeoff by
prior to flight.
the tower, the landing lights and taxi lights should be
turned ON and the airplane lined up with the centerline
The parking ramp should be examined prior to enter-
of the runway. If the runway does not have centerline
ing the airplane. During the day, it is quite easy to see
lighting, use the painted centerline and the runway-
stepladders, chuckholes, wheel chocks, and other
edge lights. After the airplane is aligned, the heading
obstructions, but at night it is more difficult. Acheck
indicator should be noted or set to correspond to the
of the area can prevent taxiing mishaps.
known runway direction. To begin the takeoff, the
S brakes should be released and the throttle smoothly
TARTING,TAXIING,AND RUNUP
advanced to maximum allowable power. As the air-
After the pilot is seated in the cockpit and prior to start-
plane accelerates, it should be kept moving straight
ing the engine, all items and materials to be used on the
ahead between and parallel to the runway-edge lights.
flight should be arranged in such a manner that they
will be readily available and convenient to use. The procedure for night takeoffs is the same as for nor-
mal daytime takeoffs except that many of the runway
Extra caution should be taken at night to assure the
visual cues are not available. Therefore, the flight
propeller area is clear. Turning the rotating beacon ON,
instruments should be checked frequently during the
or flashing the airplane position lights will serve to
takeoff to ensure the proper pitch attitude, heading, and
alert persons nearby to remain clear of the propeller.
airspeed are being attained. As the airspeed reaches the
To avoid excessive drain of electrical current from the
normal lift-off speed, the pitch attitude should be
battery, it is recommended that unnecessary electrical
adjusted to that which will establish a normal climb.
equipment be turned OFF until after the engine has
This should be accomplished by referring to both out-
been started.
side visual references, such as lights, and to the flight
instruments. [Figure 10-3]
After starting and before taxiing, the taxi or landing
light should be turned ON. Continuous use of the land-
ing light with r.p.m. power settings normally used for
taxiing may place an excessive drain on the airplane’s
electrical system. Also, overheating of the landing light
could become a problem because of inadequate airflow
to carry the heat away. Landing lights should be used
as necessary while taxiing. When using landing lights,
consideration should be given to not blinding other
pilots. Taxi slowly, particularly in congested areas. If
taxi lines are painted on the ramp or taxiway, these
lines should be followed to ensure a proper path along
the route.
The before takeoff and runup should be performed
using the checklist. During the day, forward movement Figure 10-3.Establish a positive climb.
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After becoming airborne, the darkness of night often preplanning is adequate, and the pilot continues to
makes it difficult to note whether the airplane is get- monitor position, time estimates, and fuel consumed.
ting closer to or farther from the surface. To ensure the NAVAIDs, if available, should be used to assist in
airplane continues in a positive climb, be sure a climb monitoring en route progress.
is indicated on the attitude indicator, vertical speed
indicator (VSI), and altimeter. It is also important to Crossing large bodies of water at night in single-
ensure the airspeed is at best climb speed. engine airplanes could be potentially hazardous, not
only from the standpoint of landing (ditching) in the
Necessary pitch and bank adjustments should be made water, but also because with little or no lighting the
by referencing the attitude and heading indicators. It is horizon blends with the water, in which case, depth
recommended that turns not be made until reaching a perception and orientation become difficult. During
safe maneuvering altitude. poor visibility conditions over water, the horizon will
become obscure, and may result in a loss of orienta-
Although the use of the landing lights provides help tion. Even on clear nights, the stars may be reflected
during the takeoff, they become ineffective after the on the water surface, which could appear as a contin-
airplane has climbed to an altitude where the light uous array of lights, thus making the horizon difficult
beam no longer extends to the surface. The light can to identify.
cause distortion when it is reflected by haze, smoke, or
fog that might exist in the climb. Therefore, when the Lighted runways, buildings, or other objects may
landing light is used for the takeoff, it may be turned cause illusions to the pilot when seen from different
off after the climb is well established provided other altitudes. At an altitude of 2,000 feet, a group of lights
traffic in the area does not require its use for collision on an object may be seen individually, while at 5,000
avoidance. feet or higher, the same lights could appear to be one
solid light mass. These illusions may become quite
O
RIENTATION AND NAVIGATION acute with altitude changes and if not overcome could
Generally, at night it is difficult to see clouds and present problems in respect to approaches to lighted
restrictions to visibility, particularly on dark nights or runways.
under overcast. The pilot flying under VFR must exer-
A
cise caution to avoid flying into clouds or a layer of PPROACHES AND LANDINGS
fog. Usually, the first indication of flying into restricted When approaching the airport to enter the traffic pat-
visibility conditions is the gradual disappearance of tern and land, it is important that the runway lights
lights on the ground. If the lights begin to take on an and other airport lighting be identified as early as
appearance of being surrounded by a halo or glow, the possible. If the airport layout is unfamiliar to the
pilot should use caution in attempting further flight in pilot, sighting of the runway may be difficult until
that same direction. Such a halo or glow around lights very close-in due to the maze of lights observed in
on the ground is indicative of ground fog. Remember the area. [Figure 10-4] The pilot should fly toward
that if a descent must be made through fog, smoke, or the rotating beacon until the lights outlining the run-
haze in order to land, the horizontal visibility is consid- way are distinguishable. To fly a traffic pattern of
erably less when looking through the restriction than it proper size and direction, the runway threshold and
is when looking straight down through it from above. runway-edge lights must be positively identified.
Under no circumstances should a VFR night-flight be Once the airport lights are seen, these lights should
made during poor or marginal weather conditions be kept in sight throughout the approach.
unless both the pilot and aircraft are certificated and
equipped for flight under instrument flight rules (IFR).
The pilot should practice and acquire competency in
straight-and-level flight, climbs and descents, level
turns, climbing and descending turns, and steep turns.
Recovery from unusual attitudes should also be prac-
ticed, but only on dual flights with a flight instructor.
The pilot should also practice these maneuvers with all
the cockpit lights turned OFF. This blackout training is
necessary if the pilot experiences an electrical or
instrument light failure. Training should also include
using the navigation equipment and local NAVAIDs.
In spite of fewer references or checkpoints, night cross-
country flights do not present particular problems if
Figure 10-4.Use light patterns for orientation.
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Distance may be deceptive
Above Glidepath Below Glidepath On Glidepath
at night due to limited
lighting conditions. Alack
of intervening references
on the ground and the
inability of the pilot to com-
pare the size and location of
different ground objects
cause this. This also applies
to the estimation of altitude
and speed. Consequently,
more dependence must be
placed on flight instruments,
particularly the altimeter and
If both light bars are white, If you see red over red, you If the far bar is red and the
the airspeed indicator. you are too high. are below the glidepath. near bar is white, you are on
the glidepath. The memory
aid "red over white, you're all
When entering the traffic
right," is helpful in recalling
pattern, allow for plenty of the correct sequence of lights.
time to complete the
Figure 10-5.VASI.
before landing checklist. If
the heading indicator contains a heading bug, setting it height for the correct roundout. To aid in determining
to the runway heading will be an excellent reference the proper roundout point, continue a constant
for the pattern legs. approach descent until the landing lights reflect on the
runway and tire marks on the runway can be seen
Every effort should be made to maintain the recom- clearly. At this point the roundout should be started
mended airspeeds and execute the approach and smoothly and the throttle gradually reduced to idle
landing in the same manner as during the day. Alow, as the airplane is touching down. [Figure 10-6]
shallow approach is definitely inappropriate during During landings without the use of landing lights, the
a night operation. The altimeter and VSI should be roundout may be started when the runway lights at the
constantly cross-checked against the airplane’s position
along the base leg and final approach. A visual
approach slope indicator (VASI) is an indispensable aid
in establishing and maintaining a proper glidepath.
[Figure 10-5]
After turning onto the final approach and aligning the
airplane midway between the two rows of runway-edge
lights, the pilot should note and correct for any wind
drift. Throughout the final approach, pitch and power
should be used to maintain a stabilized approach. Flaps
should be used the same as in a normal approach.
Usually, halfway through the final approach, the land-
ing light should be turned on. Earlier use of the landing
light may be necessary because of “Operation Lights
ON” or for local traffic considerations. The landing
light is sometimes ineffective since the light beam will
usually not reach the ground from higher altitudes. The
light may even be reflected back into the pilot’s eyes
by any existing haze, smoke, or fog. This disadvantage
is overshadowed by the safety considerations provided
by using the “Operation Lights ON” procedure around
other traffic.
The roundout and touchdown should be made in the
same manner as in day landings. At night, the judg-
ment of height, speed, and sink rate is impaired by the
scarcity of observable objects in the landing area. The
inexperienced pilot may have a tendency to round out
too high until attaining familiarity with the proper Figure 10-6.Roundout when tire marks are visible.
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far end of the runway first appear to be rising higher • Announce the emergency situation to Air Traffic
than the nose of the airplane. This demands a smooth Control (ATC) or UNICOM. If already in radio
and very timely roundout, and requires that the pilot contact with a facility, do not change frequen-
feel for the runway surface using power and pitch cies, unless instructed to change.
changes, as necessary, for the airplane to settle slowly
to the runway. Blackout landings should always be • If the condition of the nearby terrain is known,
included in night pilot training as an emergency turn towards an unlighted portion of the area.
procedure. Plan an emergency approach to an unlighted
portion.
N
IGHT EMERGENCIES
Perhaps the pilot’s greatest concern about flying a single- • Consider an emergency landing area close to
engine airplane at night is the possibility of a complete public access if possible. This may facilitate
engine failure and the subsequent emergency landing. rescue or help, if needed.
This is a legitimate concern, even though continuing
flight into adverse weather and poor pilot judgment • Maintain orientation with the wind to avoid a
account for most serious accidents. downwind landing.
If the engine fails at night, several important procedures • Complete the before landing checklist, and
and considerations to keep in mind are: check the landing lights for operation at altitude
and turn ON in sufficient time to illuminate the
• Maintain positive control of the airplane and terrain or obstacles along the flightpath. The
establish the best glide configuration and airspeed. landing should be completed in the normal land-
Turn the airplane towards an airport or away from ing attitude at the slowest possible airspeed. If
congested areas. the landing lights are unusable and outside visual
references are not available, the airplane should
• Check to determine the cause of the engine be held in level-landing attitude until the ground
malfunction, such as the position of fuel selec- is contacted.
tors, magneto switch, or primer. If possible, the
cause of the malfunction should be corrected • After landing, turn off all switches and evacuate
immediately and the engine restarted. the airplane as quickly as possible.
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H attempts have been made to compromise this
IGH PERFORMANCE AND COMPLEX
conflicting requirement of high cruise and slow
AIRPLANES landing speeds.
Transition to a complex airplane, or a high performance
airplane, can be demanding for most pilots without pre- Since an airfoil cannot have two different cambers at
vious experience. Increased performance and increased the same time, one of two things must be done. Either
complexity both require additional planning, judgment, the airfoil can be a compromise, or a cruise airfoil can
and piloting skills. Transition to these types of be combined with a device for increasing the camber of
airplanes, therefore, should be accomplished in a the airfoil for low-speed flight. One method for varying
systematic manner through a structured course of an airfoil’s camber is the addition of trailing edge flaps.
training administered by a qualified flight instructor. Engineers call these devices a high-lift system.
Acomplex airplane is defined as an airplane equipped FUNCTION OF FLAPS
with a retractable landing gear, wing flaps, and a Flaps work primarily by changing the camber of the
controllable-pitch propeller. For a seaplane to be airfoil since deflection adds aft camber. Flap deflection
considered complex, it is required to have wing flaps and does not increase the critical (stall) angle of attack, and
a controllable-pitch propeller. A high performance in some cases flap deflection actually decreases the
airplane is defined as an airplane with an engine of more critical angle of attack.
than 200 horsepower.
Deflection of trailing edge control surfaces, such as the
W
ING FLAPS aileron, alters both lift and drag. With aileron
Airplanes can be designed to fly fast or slow. High deflection, there is asymmetrical lift (rolling moment)
speed requires thin, moderately camberedairfoils with and drag (adverse yaw). Wing flaps differ in that
a small wing area, whereas the high lift needed for low deflection acts symmetrically on the airplane. There is
speeds is obtained with thicker highly cambered no roll or yaw effect, and pitch changes depend on the
airfoils with a larger wing area. [Figure 11-1] Many airplane design.
Tapered
Elliptical
Sweptback
Straight
Delta
Figure 11-1.Airfoil types.
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Ch 11.qxd 5/7/04 8:50 AM Page 11-2
Pitch behavior depends on flap type, wing position,
and horizontal tail location. The increased camber
from flap deflection produces lift primarily on the rear
portion of the wing. This produces a nosedown
pitching moment; however, the change in tail load
from the downwash deflected by the flaps over the
horizontal tail has a significant influence on the Plain Flap
pitching moment. Consequently, pitch behavior
depends on the design features of the particular airplane.
Flap deflection of up to 15° primarily produces lift
with minimal drag. The tendency to balloon up with
initial flap deflection is because of lift increase, but the
nosedown pitching moment tends to offset the balloon.
Deflection beyond 15° produces a large increase in Split Flap
drag. Drag from flap deflection is parasite drag, and
as such is proportional to the square of the speed. Also,
deflection beyond 15° produces a significant noseup
pitching moment in most high-wing airplanes because
the resulting downwash increases the airflow over the
horizontal tail.
FLAP EFFECTIVENESS
Slotted Flap
Flap effectiveness depends on a number of factors, but
the most noticeable are size and type. For the purpose
of this chapter, trailing edge flaps are classified as four
basic types: plain (hinge), split, slotted, and Fowler.
[Figure 11-2]
The plain or hinge flap is a hinged section of the wing.
The structure and function are comparable to the other
control surfaces—ailerons, rudder, and elevator. The
Fowler Flap
split flap is more complex. It is the lower or underside
portion of the wing; deflection of the flap leaves the
trailing edge of the wing undisturbed. It is, however,
more effective than the hinge flap because of greater Figure 11-2.Four basic types of flaps.
lift and less pitching moment, but there is more drag.
Split flaps are more useful for landing, but the partially system does, however, give the maximum lift
deflected hinge flaps have the advantage in takeoff. coefficient. Drag characteristics at small deflections
The split flap has significant drag at small deflections, are much like the slotted flap. Because of structural
whereas the hinge flap does not because airflow complexity and difficulty in sealing the slots, Fowler
remains “attached” to the flap. flaps are most commonly used on larger airplanes.
The slotted flap has a gap between the wing and the OPERATIONAL PROCEDURES
leading edge of the flap. The slot allows high It would be impossible to discuss all the many airplane
pressure airflow on the wing undersurface to energize design and flap combinations. This emphasizes the
the lower pressure over the top, thereby delaying flow importance of the FAA-approved Airplane Flight
separation. The slotted flap has greater lift than the Manual and/or Pilot’s Operating Handbook
hinge flap but less than the split flap; but, because of (AFM/POH) for a given airplane. However, while
a higher lift-drag ratio, it gives better takeoff and some AFM/POHs are specific as to operational use of
climb performance. Small deflections of the slotted flaps, many are lacking. Hence, flap operation makes
flap give a higher drag than the hinge flap but less pilot judgment of critical importance. In addition, flap
than the split. This allows the slotted flap to be used operation is used for landings and takeoffs, during
for takeoff. which the airplane is in close proximity to the ground
where the margin for error is small.
The Fowler flap deflects down and aft to increase the
wing area. This flap can be multi-slotted making it the Since the recommendations given in the AFM/POH are
most complex of the trailing edge systems. This based on the airplane and the flap design combination,
11-2
Description:NIGHT VISION. Generally, most pilots are poorly informed about night vision.
Human eyes never function as effectively at night as the eyes of animals with
